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The methodologies and status of the Host-Mediated Assay were reviewed using the published literature available up to June 1980. The Working Group reviewed 274 documents, including abstracts, research articles, review articles, and publicly available contracts and grant final reports. From this group, abstracts and reviews were rejected from critical evaluation. 77 documents were accepted and reviewed by the Working Group and the test results summarized. These selected documents yielded 208 chemicals that were evaluated in th host-mediated assay. Of these chemicals, 133 were mutagenic in this assay with one or more indicators. 76 chemicals, several of which are not considered to be carcinogenic, were not detected by any of the indicators. Of the 208 chemicals, 125 had been tested in carcinogenicity assay in rodents. 90, or 71%, of the carcinogens were detected as mutagens in the Host-Mediated Assay. In several cases, those carcinogens not detected may have been negative because of improper selection of the indicator. The Working Group concluded that the Host-Mediated Assay is an important test in mutagenicity/carcinogenicity research and that, by proper selection of protocols and indicators, valuable information can be gained that otherwise would be overlooked strict, in vitro assays.
The common onion (Allium cepa) is an excellent plant for the assay of chromosome aberrations after chemical treatment. Other species of allium (A. cepa var. proliferum, A. carinatum, A. fistulosum and A. sativum) have also been used but to a much lesser extent. Protocols have been given for using root tips from either bulbs or seeds of Allium cepa to study the cytological end-points, such as chromosome breaks and exchanges, which follow the testing of chemicals in somatic cells. It is considered that both mitotic and meiotic end-points should be used to a greater extent in assaying the cytogenetic effects of a chemical. From a literature survey, 148 chemicals are tabulated that have been assayed in 164 Allium tests for the clastogenic effect. Of the 164 assays which have been carried out, 75 are reported as giving a positive reaction (i.e., causing chromosome aberrations), 49 positive and with a dose response, 1 positive and temperature-related, 9 borderline positive, and 30 negative; 76% of the chemicals gave a definite positive response. It is proposed that the Allium test be included among those tests routinely used for assessing chromosomal damage induced by chemicals.
The use of the angiosperm Zea mays in assays for the induction of mutations at specific genetic loci is discussed. The effect of chemical mutagens on 3 genetic end points is evaluated. The end points surveyed were the loss of the phenotype of dominant alleles in heterozygotes, the induction of segregating point mutations in M2 plants, and the induction of forward and reverse mutations in pollen grains. Maize is sensitive to a wide range of mutagens and has the capacity to activate promutagens. This plant has been used to study mutagenesis under both laboratory and in situ conditions.
The literature on the mouse sperm morphology test and on other sperm tests in nonhuman mammals was reviewed (a) to evaluate the relationship of these tests to chemically induced spermatogenic dysfunction, germ-cell mutagenicity, and carcinogenicity, and (b) to make an interspecies comparison to chemicals. A total of 71 papers were reviewed. The mouse sperm morphology test was used to assess the effects of 154 of the 182 chemical agents covered. 4 other murine sperm tests were also used: the induction of acrosomal abnormalities (4 agents), reduction in sperm counts, (6 agents), motility (5 agents), and F1 sperm morphology (7 agents)). In addition, sperm tests for the spermatogenic effects of 35 agents were done in 9 nonmurine mammalian species; these included analyses for sperm count, motility, and morphology, using a large variety of study designs. For the mouse sperm morphology test, 41 agents were judged by the reviewing committee to be positive inducers of sperm-head shape abnormalities, 103 were negative, and 10 were inconclusive. To evaluate the relationship between changes in sperm morphology and germ cell mutagenicity, the effects of 41 agents on mouse sperm shape were compared to available data from 3 different mammalian germ-cell mutational tests (specific locus, heritable translocation, and dominant lethal). The mouse sperm morphology test was found to be highly sensitive to germ-cell mutagens; 100% of the known mutagens were correctly identified as positives in the sperm morphology test. Data are insufficient at present to access the rate of false positives. Although it is biologically unclear why one might expect changes in sperm morphology to be related to carcinogenesis, we found that (a) a positive response in the mouse sperm morphology test is highly specific for carcinogenic potential (100% for the agents surveyed), and (b) overall, only 50% of carcinogens were positive in the test (i.e., sensitivity approximately equal to 50%). Since many carcinogens do not produce abnormally shaped sperm even at lethal doses, negative findings with the sperm test cannot be used to classify agents as noncarcinogens. We conclude that the mouse sperm morphology test has potential use for identifying chemicals that induce spermatogenic dysfunction and perhaps heritable mutations. Insufficient numbers of chemicals agents have been studied by the other sperm tests to permit similar comparisons. A comparison of 25 chemicals tested with sperm counts, motility, and morphology in at least 2 species (including man, mouse and 9 other mammals) demonstrated good agreement in response among species. With further study, interspecies comparisons of chemically induced sperm changes may be useful for predicting and evaluating human effects.
The yeast Saccharomyces cerevisiae is a unicellular fungus that can be cultured as a stable haploid or a stable diploid . Diploid cultures can be induced to undergo meiosis in a synchronous fashion under well-defined conditions. Consequently, yeasts can be used to study genetic effects both in mitotic and in meiotic cells. Haploid strains have been used to study the induction of point mutations. In addition to point mutation induction, diploid strains have been used for studying mitotic recombination, which is the expression of the cellular repair activities induced by inflicted damage. Chromosomal malsegregation in mitotic and meiotic cells can also be studied in appropriately marked strains. Yeast has a considerable potential for endogenous activation, provided the tests are performed with appropriate cells. Exogenous activation has been achieved with S9 rodent liver in test tubes as well as in the host-mediated assay, where cells are injected into rodents. Yeast cells can be recovered from various organs and tested for induced genetic effects. The most commonly used genetic end point has been mitotic recombination either as mitotic crossing-over or mitotic gene conversion. A number of different strains are used by different authors. This also applies to haploid strains used for monitoring induction of point mutations. Mitotic chromosome malsegregation has been studied mainly with strain D6 and meiotic malsegregation with strain DIS13 . Data were available on tests with 492 chemicals, of which 249 were positive, as reported in 173 articles or reports. The genetic test/carcinogenicity accuracy was 0.74, based on the carcinogen listing established in the Gene-Tox Program. The yeast tests supplement the bacterial tests for detecting agents that act via radical formation, antibacterial drugs, and other chemicals interfering with chromosome segregation and recombination processes.
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Glyphosate is among the pesticides most frequently reported to the California EPA Pesticide Illness Surveillance Program. We analyzed glyphosate-related calls to the Pesticide Illness Surveillance Program in order to assess the number of reports involving systemic symptoms and to better understand the nature and severity of reported cases. Data on glyphosate and other pesticides are available for the years 1982-1997 including: type of exposure (agricultural/other); target organ(s) affected (skin/eye/respiratory/systemic); exposure(s); an assessment of causal relationship (possible, probable, or definite); and limited medical text. Of 815 total glyphosate calls, most involved topical irritation of the eye (n = 399), skin (n = 250), upper airway (n = 7), or combinations of these sites (n = 32) without systemic symptoms. Of the 187 systemic cases, only 22 had symptoms recorded as probably or definitely related to glyphosate exposure alone. The reported symptoms were not severe, expected to be limited in duration, and frequently inconsistent with the route of exposure and/or previous experience with glyphosate. We conclude that call volume is not a reliable indicator of the actual incidence or severity of glyphosate-related incidents in California.
This rule establishes consolidated permit program requirements governing the Hazardous Waste Management program under the Resource Conservation and Recovery Act (RCRA), the Underground Injection Control (UIC) program under the Safe Drinking Water Act (SDWA), the National Pollutant Discharge Elimination System (NPDES) program and State Dredge on Fill ("404") programs under the Clean Water Act (CWA), and the Prevention of Significant Deterioration (PSD) program under the Clean Air Act, for three primary purposes: (1) To consolidate program requirements for the RCRA and UIC programs with those already established for the NPDES program. (2) To establish requirements for State programs under the RCRA, UIC, and Section 404 programs. (3) To consolidate permit issuance procedures for EPA-issued Prevention of Significant Deterioration permits under the Clean Air Act with those for the RCRA, UIC, and NPDES programs.
This regulation establishes a time-limited tolerance for combined residues of avermectin in or on avocado. This action is in response to EPA's granting of an emergency exemption under section 18 of the Federal Insecticide, Fungicide, and Rodenticide Act authorizing use of the pesticide on avocado. This regulation establishes a maximum permissible level for residues of avermectin B1 and its delta-8,9-isomer in this food commodity pursuant to section 408(1)(6) of the Federal Food, Drug, and Cosmetic Act, as amended by the Food Quality Protection Act of 1996. The tolerance will expire and is revoked on September 30, 2000.
In this Final Rule, EPA is amending both the Asbestos Worker Protection Rule (WPR) and the Asbestos-in-Schools Rule. The WPR amendment protects State and local government employees from the health risks of exposure to asbestos to the same extent as private sector workers by adopting for these employees the Asbestos Standards of the Occupational Safety and Health Administration (OSHA). The WPR's coverage is extended to State and local government employees who are performing construction work, custodial work, and automotive brake and clutch repair work. This final rule cross-references the OSHA Asbestos Standards for Construction and for General Industry, so that future amendments to these OSHA standards are directly and equally effective for employees covered by the WPR. EPA also amends the Asbestos-in-Schools Rule to provide coverage under the WPR for employees of public local education agencies who perform operations, maintenance, and repair activities. EPA is issuing this final rule under section 6 of the Toxic Substances Control Act (TSCA).
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